1. Field of the Invention
The present invention relates to a photosensitive resin composition for color filters. More specifically, it relates to a photosensitive resin composition, which makes it possible to produce a color filter having less residue on an unexposed portion(s) of the substrate and the black matrix at the time of development, and provides color pixels having excellent heat resistance and chemical resistance, and provides LCD having lower electric resistance of the ITO electrode and the like, particularly a color filter for use in color liquid crystal display devices.
2. Description of Related Art
Currently, the photolithographic process is widely applied to the manufacturing of liquid crystal display (LCD). In this process, the photosensitive resin composition is first coated on a substrate and pre-baked to evaporate the solvent so as to form a coating film. Then, the coating film is exposed to UV light through a photo mask, and developed with an alkaline developer solution to dissolve and remove unexposed portions of the coating film to form an array in a predetermined pattern. The substrate is then further heated, i.e., post-bake. In general, the red, green and blue (RGB) pixels or black matrix of the color filter or cured films, such as overcoats, interlayer insulating films can be formed by such techniques.
It's necessary that the cured films aforementioned are manufactured with the procedure of high temperature (above 220° C.) or strong base or strong acid. For example, the thermal processes include forming the ITO electrodes on the surface of the RGB pixels at 230° C., or annealing the ITO electrodes at 230˜260° C. for lowering its electric resistance thereof. Therefore, how to increase the heat resistance and chemical resistance of the cured films is required.
In order to meet the above requirements, Japan Patent Publication No.1-52449 and No.9-311210 disclosed that the pixels of color filters could be manufactured by using a photosensitive resin composition comprising an alkali-soluble resin formed by copolymerization of methacrylic acid and esters of (meth)acrylate.
However, the ester functional group on the side chain of such copolymer is easily decomposed above 220° C., and the electric resistance of the ITO electrodes will be increased.
Additionally, the conventional method for producing the RGB pixels of the color filters is the dyeing process, in which the dyeing-possible resin such as natural gelatin or casein is patterned and dyed. Unfortunately, the heat resistance of these color pixels was still not satisfied by using the above process.
Recently, pigment-dispersing process is used to improve heat resistance of the cured film, and it can also provide an easier process for manufacturing the color filters.
However, it is necessary that the photosensitive resin composition is exposed and developed repeatedly during above pigment-dispersing process for color filters, and it is apt to produce a color filter having residue on an unexposed portion(s) of the substrate and the black matrix at the time of development. Therefore, further washing with a diluted developer solution or high-pressure water is required, which also complicates the manufacturing process of the color filters.